1. Field of the Invention
The present invention is directed generally to mobile wireless communication services. More particularly, the present invention is directed to a system and method for collecting data for location based services.
2. Description of the Related Art
Operators of wireless networks for mobile devices have developed several methods for determining the geographical location of a mobile station. Some methods measure the Time Difference of Arrival (TDOA) or Angle of Arrival (AOA) of a signal transmitted by a mobile station and received at multiple base stations, then use geometric algorithms to determine the location of the mobile station. However, TDOA and AOA require additional equipment to be installed and maintained at many base stations. Some methods use a Global Positioning System (GPS) receiver in each mobile station to report the position of that mobile station to the network. This has the disadvantage that it requires additional equipment in every mobile station. Additionally, GPS does not work well in some situations, particularly in urban areas where large buildings block the satellite signals.
Some methods use Received Signal Strength Indication (RSSI) measurements. Many types of mobile stations regularly make RSSI measurements of control signals from nearby base stations and send the measurements to a Mobile Switching Center (MSC) to ensure that the mobile station is connected to the network through the best available base station. Selected RSSI measurements are then routed by the MSC over a Lb link to a mobile location module (MLM) which uses the selected RSSI measurements to determine mobile station location. This method is adequate for infrequent use such as 911 calls and requests by users of mobile stations for their location. However, it does not work well with widespread use. If the network operator wants to track the location of a large number of mobile stations simultaneously and continuously, the amount of information processing could overwhelm the BSC and MSC, adversely affecting the network's ability to route voice and data traffic. Additionally, the system would need a large bandwidth connection between the MSC and MLM to handle the continuous flow of requests and measurements. What is needed is a system and method to obtain the measurements required for determining the location of a large number of mobile stations continuously without overburdening the mobile wireless network and impeding its ability to route voice and data traffic. The present invention provides this advantage and other advantages as will be apparent from the following detailed description and accompanying figures.